1. Field of the Invention
The present invention relates to a substrate processing apparatus, and more particularly to a polishing apparatus for polishing a workpiece such as a semiconductor wafer to a flat mirror finish.
2. Description of the Related Art
As semiconductor devices have become more highly integrated in recent years, circuit interconnections have become finer and distances between those circuit interconnections have become smaller. In the case of photolithography, which can form interconnections that are at most 0.5 μm wide, it is required that surfaces on which pattern images are to be focused by a stepper should be as flat as possible because a depth of focus of an optical system is relatively small. A polishing apparatus for performing chemical mechanical polishing (CMP) has been used for planarizing such a semiconductor wafer.
This type of chemical mechanical polishing (CMP) apparatus comprises a polishing table having a polishing pad (polishing cloth) attached thereon, and a top ring for holding a workpiece to be polished, such as a semiconductor wafer, in a manner such that a surface to be polished faces the polishing table. The polishing pad has an upper surface serving as a polishing surface. In this polishing apparatus, the polishing table and the top ring are independently rotated, and, while an abrasive liquid (slurry) is being supplied onto the polishing pad, a workpiece is pressed against the polishing pad on the polishing table at a predetermined pressure by the top ring. Thus, a surface of the workpiece is polished to a flat mirror finish.
In many instances, such a polishing apparatus has a plurality of cleaning devices for cleaning a wafer which has been polished. Specifically, a conventional polishing apparatus has a plurality of cleaning devices arranged in parallel with each other. Accordingly, as the number of cleaning processes increases, the length of the polishing apparatus become larger, resulting in an increased footprint of the apparatus. In order to reduce the footprint of the apparatus, it has been attempted to employ a cleaning device which can receive a wafer placed along a vertical direction. However, when a wafer is placed along a vertical direction at the time of cleaning, the cleaning performance is adversely lowered.